Hmmmm, maybe worth buying if you never played PGR3?
I don't know why, but right off the bat this game just "felt different" then PGR3. Maybe it's the night time races, or the weather effects... I don't really know. The graphics (to me) seem not as sharp as they were. Granted, the addition of weather is VERY COOL. Difficulity : Again, it seems "different" then it was. It could be just me being a little rusty, but the early levels just seem harder then they should be, I was having a hard time just finishing 3rd while in races against the AI on normal level.
Audio : This might be the only thing that does not feel different, it's great just like it was in PGR3. The sounds of the different cars/bikes really bring you into the game.
Graphics : Still good, but just seem a little on the dull side. The game runs at a very nice FPS (not sure what it is) and I have not noticed any stutter or slowdown. The inside car view is still AMAZING and is what I use about 80% of the time, it just makes it feel like you are there.
Online: Have not tried that yet, so comment
Over all this is a good arcade style racer. Lots of cars and lots of different tracks and test to complete. I say pick it up, it should give many hours of gaming enjoyment.